Method of initially placing the train and elevation axes of a gun in parallelism with the corresponding axes of the sights of its director



p 1949- c. G. WILLIAMS 2,48 ,551

METHOD OF INITIALLY PLACING THE TRAIN AND ELEVATION AXES OF A GUN IN PARALLELISM WITH THE CORRESPONDING AXES OF THE SIGHTS OF ITS DIRECTOR Filed March 29, 1946 1 Craig [3 .Williams A gww v/XJZJWM Patented Sept. 13, 1949 METHOD OF INITIALLY PLACING THE TRAIN AND ELEVATION AXES OF A GUN IN PAR- ALLELISM WITH THE CORRESPONDING AXES OF THE SIGHTS OF ITS DIRECTOR Craig G. Williams, Schenectady, N. Y.

Application March 29, 1946, Serial No. 658,198

2 Claims. (01. 88-1) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Gevernment for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to optical instruments and a method for locating the pivot axes of two objects in parallelism. A specific example of the use of the invention is given in the following paragraphs in connection with the placing of the trunnion axis and bore of a un in parallelism with the axis of elevation and line of sight, respectively, of the sights of a director to be used in aiming the gun.

It is customary to automatically, or semi-automatically, effect the control of large calibre guns from a so-called director. The director is, actually, a complicated computer into which are set various values, the more important of which are azimuth and elevation of the line of sight to a target from the director, rate of movement in azimuth and elevation of said line of sight, and range. The director takes these input values, and from them computes and delivers data necessary for the correct aiming of the gun to hit the target sighted through the director telescopes or radar equipment. The director and gun may be separated by a few feet and the data mentioned are transmitted to the gun over conventional electric teiemetric systems and there used as a basis for laying the gun. Actual movement of the gun may be effected either (a) automatically as through the use of power follow-ups or servomotors, (b) by direct manual actuation of the gun in accordance with indications transmitted from the director or (c) by manual control of motors connected to train and elevate the gun and in accordance with the aforesaid data re ceived from the director. The angular values received from the director continuously change in the case of a moving target such as an aircraft and, when the gun is smoothly operated in accordance with those values, it is continuously aimed to hit the target and may be fired at any time ordered by the battery commander.

One type of a widely used director consists of a box-like casing supported on a tripod for pivotal movement about a vertical axis. A first or trainers sight is mounted on one vertical side of the casing and a second or elevators sight is mounted on the opposite side. The lines of sight determined by these two sights are parallel and they are connected for movement in unison relatively to the director casing about a horizontal or elevation axis normal to their lines of sight. The trainer then operates controls moving the entire director andboth sights about the aforesaid vertical axis to keep the vertical cross-hair of his telescope on the target. The elevator operates controls moving both telescopes about the aforesaid horizontal or elevation axis to keep the horizontal cross hair of this telescope upon the target.

When other values are correctly set into the director, it affords an ouput (a) of an azimuth angle measured from a horizontal line having a definite fixed direction and (b) of an elevation angle measured with respect to a horizontal line normal to the aforesaid elevation axes of the telescopes. Since these output angular values are thus measured from definite base lines, it is necessary that the director be initially so placed and adjusted that (a) the aforesaid horizontal axis or axes about which the sighting telescopes are elevated, is exactly parallel with the axis of the gun trunnions and (b) the lines of sight of the telescopes are parallel with the axis of the gun bore in the zero elevation position of the gun. Then, when the gun is moved about train and elevation axes as measured from said base lines, in accordance with the respective output values of the director, the gun is properly aimed to hit the target sighted. It should be understood, however, that this parallelism of the respective axes is not maintained during firing. In fact, the main purpose of the director is to determine the horizontal and vertical angles by which the gun bore should lead the line of sight to the target in order that the projectile may intersect the target at its position after the time necessary for the projectile to travel from gun to target.

It is therefore an object of my invention to provide a method by which the aforesaid gun trunnion and bore axes, may be quickly and easily initially parallelized with the corresponding axes of the director sights.

A further object is to provide a method as aforesaid that does not require the provision of remote sighting stakes or the insertion of parts into the gun bore as with previous methods and devices.

Another object is to provide a method as aforesaid that is highly accurate, and one which can be carried out by apparatus which is easy and inexpensive to construct and which, at the same time enables the aforesaid alignment and subsequent check alignments to be accomplished in a time substantially less than that required by prior art methods.

A still further object is to afford a method of effecting parallelism between axes, that does not require exposure of the gun crew to enemy fire as the case with prior art methods.

A further object is to provide a method which can be quickly and easily learned by the gun crew, and one which minimizes leveling errors by orienting at center of field of fire.

Other objects and advantages of the invention will become apparent as the description proceeds.

In the drawings:

Figure 1 is a schematic View showing the use of the invention in effecting parallelism between the common horizontal or elevation axis of the sights and the axis of the gun trunnions.

Figure 1a is a view showing the view through the trainers telescope when sighting is effected by the use of an extra cross-hair positioned within the telescope.

Figure lb'is a view similar to Figure 10. showing the appearance of the reflected image when using a disc with a small central aperture in position over the objective end of the telescope.

Figure 2 is a schematic view showing the use of the invention in effecting parallelism between the elevation or pointers telescope and the axis of the gun bore.

Figure 2a shows the view through the pointers telescope when sighting is eflected by the use of an extra cross-hair positioned within the telescope.

Figure 2b is a view similar to Figure 2a showing the appearance of the reflected image when using a disc with a small central aperture in position over the objective end of the telescope.

Figure 3 is a longitudinal cross section through the mirror and tube forming a part of the invention.

Figure 4 is a diametral cross section of a pentaprism and holder, forming another part of the invention.

Figure 5 is a perspective view of a holder for a cross-hair adapted to be inserted in the director telescopes.

Figure 6 is a section taken upon the line 6-6, of Figure 3 showing the relative disposition of the supporting screws.

Referring to Figure 1, I indicates a gun which.

may be a mm. antiaircraft weapon having a breech casing indicated generally at 2. This casing carries aligned trunnions 3 which define a normally horizontal elevation axis of the gun and are journaled in bearings carried by a top carriage 36. This top carriage is journaled in a lower carriage for pivotal movement about a normally vertical axis The gun is shown elevated to approximately 90" and it is assumed that a machined upper or top surface 4 of casing 2, is parallel both to the axis of the gun bore and to the axis of trunnions 3. Such a surface is provided on guns of the type shown for the reception and support of a gunners quadrant.

A director is indicated generally at 5 and includes a housing 6 pivoted on a base I for movement about a vertical axis. Base 1 may be supported by a tripod 8 including platform 1' and leveling means 9 by which the base may be leveled and the aforesaid axis rendered truly vertical. A trainer's telescope I0 is carried on housing 6 for movement about a horizontal axis I I, normal to the plane of the paper. The telescope is of the prime or elbow type so that the trainer, by looking into eyepiece I 2 and manipulating handwheel !3 may cause the entire director housing and parts carried thereby, to rotate about the vertical axis to direct the line of sight into any desired direction in azimuth.

The numeral l4 indicates generally one of the component units of my invention. Referring to Figure 3, it will be noted that this unit comprises a cylindrical casing I5 counterbored at one end to form a shoulder IS. A plane mirror I! fits within the counterbore and. has its perimeter held in contact with the shoulder by means of a raised rim portion IQ of a retainer I8, threadedly engaging the casing l5. A fiber disc '20 may be interposed between the mirror and plug to prevent damage to the mirror during assembly. The cylinder l5 may be reduced in diameter externally between its ends, as indicated at 26. A pair of screws 34 and 35, Figure 6, may be threaded into circumferentially spaced apertures in the cylinder. The relation of the parts is such that the heads of screws 34 and 35 are coplanar with an intermediate element of the cylinder so that the latter will rest, without rolling, upon a flat surface and with the aforesaid element of the cylinder in contact with said surface. The purpose of this will be subsequently described. The mirror I! and rim of casing l5 adjacent retainer l8 lie in parallel planes exactly normal to the axis of the cylindrical casing.

The end of cylindrical casing l5 opposite mirror ll may be provided with a threaded counterbore 21 adapted to receive the threaded portion of a second unit 22, shown in cross section at Figure 4. Unit 22 has a central aperture 23 flared as at 24 to provide a sight opening. A pentaprism 25 is secured to unit 22, with one transmitting face over aperture 23 so that the line of sight through the aperture is deflected at and parallel to the two faces of the unit. The two units are always separated in actual use, but may be screwthreadedly united, as indicated in dotted lines, Figure 3, for protection of the prism and to insure against separation and loss of the parts.

The unit 22 is of a size such that its flat rim portion opposite prism 25 may rest squarely upon, and be supported by, the objective end of the elevation telescope 21, as shown upon Figure 2. In this position, the unit establishes a line of sight that is precisely at right angles to the normal line of sight of the telescope.

Figure 5 shows a collar 30 having a flange 3|. A small pane of glass or transparent plastic 32 fits and is held within the collar in any suitable manner as by an internal flange and retainer ring. A diametral line 33 is scribed on the pane. The flange is adapted to snugly fit within the telescopes so as to remain in adjusted position during parallelizing of gun and director, and also during normal operation.

While the dimensions of the parts is subject to wide variation and will, in certain instances, depend upon the dimensions of the director telescopes, a model found very satisfactory in use with a 40 mm. antiaircraft gun and an M5 director, consisted of a cylinder 2%" outside diameter and 3" long. The mirror may be of 4" plate :plass and plug l8 about 2.18 diameter with 32 threads per inch. Holes 28 are provided for a spanner.

In using the device for parallelizing the trunnion axis of the gun with the elevation axis of the director telescopes, the gun and director are located in their desired relative positions. The appropriate leveling means of both gun and director are operated to render their train axes vertical in which case, of course, the trunnion axis of the gun and elevation axis ll of the director are horizontal. The gun is then moved in train until it lies substantially in the vertical tical cross hair of the telescope.

SEARQH Emit plane through the gun and director and pointed away from the director. Likewise, the director is slewed until the line of sight of the azimuth or trainers telescope lies in the aforesaid plane and is directed toward the gun. The gun is then elevated approximately 90 to a vertical position so that its surface 4 is substantially perpendicular and casing I5 is held firmly thereagainst. The director and gun are now given final adjustments until the vertical diametral hair line 33 of the telescope attachment is in exact alignment with the image thereof as reflected by mirror H. The 'view as seen through ocular l2, will then appear as in Figure 1a. In some cases it may be preferable to use a cap or mask having a small central aperture about in diameter and adapted to fit over the objective end of telescope l0. When such'a cap or mask is used, the view will appear as in Figure lb, with the image of the aforesaid central aperture as reflected by mirror I I, exactly bisected by the ver- It should be noted that it is not necessary that the image be exactly at the center of the .cross hair so long as the two are superimposed.

Under the conditions of adjustment just described, the axis II is parallel to the axis of trunnions 3. The azimuth clutch connecting the mechanism by which handwheel l3 trains the director housing 6 is now closed as well as the telemetric mechanism by which the director indicates or controls the necessary azimuthal or train position of the gun. Thereafter, the azimuth output angles of the director are with reference to a base line having the same direction as the corresponding base line of the gun and the gun is, in all cases, properly trained when it is turned from the base line just determined, by the azimuth angle predicted by the director.

The gun is maintained in its position of approximately 90 elevation and after disconnection of the elevation clutch of the director, the telescopes are inoved to substantially vertical position, as shown for telescope 21, Figure 2. Unit 22 is placed in position supported by the objective end of telescope 21, with the objective or receiving face of pentaprism 25 toward the director. Since the axis of trunnions 3 and axis I l are parallel, the gun and telescopes are adjusted about these axes until the reflection of the objective of telescope 21 is seen by an observer looking through ocular 29. When the relation has been established, the appearance will be as shown at Figure 2a in case a special reticle is used, and as shown at Figure 2b in event an aperture cap or plate is employed. In each case the lines of sight and of reflection, are coincident and since surface 4 is parallel to the axis of the gun bore, mirror I! is likewise parallel to said axis and the lines of sight and reflection are at 90 thereto. These lines are also known to be at 90 to the optical axis of telescope 21. Hence the said optical axis is parallel to the gun bore. The unit 22 is removed and both sights and gun are telemetrically connected and lowered in synchronism to the point blank, or zero elevation angle of the gun. The director sights are then connected to the computing mechanism by means that are a part of the director. The axis of the gun bore and telescopes are now parallel in the zero elevation position of thegun, and all elevation angles predicted by the director are with reference to this gun position so that the gun is properly elevated in accordance with the predicted elevation angle of the director.

After this adjustment the gun and its director are properly related for accurate firing. The entire operation may be performed in about two minutes.

While the unit 22 with pentaprism 25 is a preferred form of means for 'parallelizing the gun bore with the elevation telescope, the mirror device of Figure 3 may be used for this purpose by lowering the gun to a position in which the plane of surface 4 intersects the director axis H. The casing I5 is now held on said surface in the position shown at Figure 6, with mirror ll facing the director. In this position, the mirror is at right angles to surface 4. The telescope 21 is adjusted to sight upon the mirror and the gun is adjusted in elevation until the images appear as in Figure 2a or 2?) and it is thus known that the line of sight and coincident line or reflection, are normal to the plane of the mirror and, since the axis of the gun trunnions and axis H are parallel by the previous adjustment, the line of Zight is necessarily parallel to the axis of the ore.

Either method may be used in bringing the elevation telescope and bore into parallelism and it is my intention that unit 22 shall be provided with pentaprism 25 as well as screws 34 and 35 so that either method may be used as the exigencies of the situation dictate.

It is contemplated that the method may be practiced using a specially prepared surface either on the gun tube itself or on its breech casing, parallel to the elevation and bore axes. Alternatively a special holder may be provided on the gun and adapted to receive a plane mirror and to locate the same in either of two definite positions. In the first position the mirror will be parallel to the elevation and bore axes of the gun. In the second position, the mirror will be parallel to the elevation axis and normal to the bore axis.

As an alternative to the use of a special crosshair attachment, as shown in Figure 5, or a mask or cap having a small central aperture fitting over the objective of the telescopes, a lens may be placed over the objective end of the telescopes. Such lens should have a focal length equal to approximately twice the distance from the telescopes to the mirror on the gun. Since the director is usually 11 to 13 feet from the gun, a lens having a focal length of 260" to 320 will operate satisfactorily. Such a lens causes the plane of the image to more nearly coincide with the sighting cross-hairs of the telescope and enables a very close alignment between said hairs and their image as reflected from the mirror.

While the invention has been described in connection with alignment of corresponding axes of a gun and independently mounted sighting telescopes, it will be clear that it is not limited to such use but may be employed with equal facility to establish parallelism between a line of sight or a pivot axis normal thereto, and respective axes of a remote and independent object. Or, in general, the invention is of use in determining parallelism between any two spaced axes where a reference surface parallel to one axis is available and a sight may be attached to the other axis so that its line of sight lies in a plane normal to said other axis.

While I have disclosed a preferred form of the method for practicing the same, together with a number of alternatives, numerous other changes, modifications and substitutions of equivalents, will be obvious to those skilled in the art after a study of the present disclosure. This disclosure should therefore be taken in an illustrative, rather than a limiting sense. It is my desire and intention to reserve all such alternative constructions and steps as fall within the scope of the subjoined claims.

Having now fully disclosed my invention, what I claim and desire to secure by Letters Patent is:

1. That method of parallelizing the horizontal levation and bore axes of a gun with the horizontal elevation axis and line of sight, respectively, of a telescope of a remote director horizontally spaced therefrom, said gunand director being rotatable about Vertical, spaced, train axes, comprising, moving said elevation axes into approximate parallelism, elevating said gun until the plane of a reflecting surface thereon parallel to the bore and elevation axes of said gun, is approximately normaht'o a line concurrent with and perpendicular to said elevation axes, pivoting such director and telescope to direct the line of sight of said telescope toward said surface, adjusting said director, telescope and gun until coincidence is effected between a reticle in said telescope and its image as reflected by said surface, as viewed through said telescope, to thereby establish precise parallelism between said elevational axes, elevating said telescope about its horizontal axis through a right angle, deflecting the line of sight of said telescope 90 in a plane normal to the horizontal axis thereof to direct the same toward said reflecting surface, and adjusting said gun and telescope about their horizontal axes, while maintaining said horizontal axes in parallelism, until coincidence is effected between the reticle in said telescope and its image as reflected by said surface when viewed through said telescope, to thereby establish prevcise parallelism between the line of sight of said telescope and the bore axis of said gun.

2. The method of parallelizing the trunnion axle of a gun with the elevation axis of the sight of a remote director, said gun and director being independently rotatable in azimuth about respec-. tive spaced normally vertical axes, comprising, adjusting said gun and director to render said normally vertical axes truly vertical to thereby render the trunnion axis of said gun and the elevation axis of the sight of said director truly horizontal, angularly moving said gun about its mutually perpendicular trunnion and vertical axes until a plane reflector fixedly supported on said gun parallel to the trunnion axis thereof is generally normal to a line connecting the gun and director, sighting through said sight on said reflector, and adjusting said gun about its vertical and trunnion axes and said director and sight about their vertical and horizontal axes, respectively, until a reticle fixed in the field of view of said sight, coincides with the image of said reticle as reflected by said plane reflector, to thereby parallelize said trunnion and elevation axes.

CRAIG G. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 527,640 Wetherill Oct. 16, 1894 1,667,995 Steinle May 1, 1928 2,124,146 Miller July 19, 1938 2,129,130 Hammer Sept. 6, 1938 2,218,884 Kellner Oct. 22, 1940 2,353,272 Simmons et al July 11, 1944 2,380,501 Christian July 31, 1945 2,410,339 Creagmile Oct. 29, 1946 FOREIGN PATENTS Number Country Date 17,371 Great Britain 1908 240,426 Great Britain Nov. 19, 1925 

